Field of the Present Disclosure
The present disclosure relates to a power wireless transmitter in a magnetic resonance-based wireless power transmission system, and, in particularly, to a power wireless transmitter in a magnetic resonance-based wireless power transmission system, wherein when, due to a presence of a metal, an output from the wireless power transmitter has a change in a resonance frequency thereof, a drive frequency and/or duty ratio with a maximum output therefrom are determined to be applied for a transmission from the wireless power transmitter, thereby to achieve an efficient wireless power transmission.
Discussion of Related Art
Generally, a magnetic resonance-based wireless power transmission system may transmit a non-radiant electronic wave energy between two resonators using resonance. When a resonance frequency of a transmitter coincides with that of a receiver, an efficient wireless power transmission may occur.
However, a resonance frequency of a transmitter does not coincide with that of a receiver, an efficient wireless power transmission may not be achieved. This is true of a situation where a metal is disposed between the transmitter and receiver due to a change in a resonance frequency.
Further, when a metal is adjacent to the wireless power transmitter, the inductance of the wireless power transmitter may change. Thus, in order to keep the resonance frequency constant, the capacitance of the wireless power transmitter may be adjusted. However, this approach may have a limitation in terms of times of the changes of the capacitance of the wireless power transmitter.
In this connection, Korean patent No. 10-1386650 discloses a method for detecting a foreign material by a wireless power transmission device in a wireless power transmission system using the magnetic resonance induction manner, as shown in FIG. 1. In this approach, when a foreign material is detected in a wireless power transmission system, it is determined whether the foreign material is a device being charged or not by transmitting a joining request signal. The method for detecting a foreign material by a wireless power transmission device in a wireless power transmission system using the magnetic resonance induction manner comprises the steps of detecting a foreign material by detecting at least one change of a current, a voltage and a phase; transmitting a joining request signal according to a magnetic field communication protocol; detecting a joining response signal which responds to the joining request signal; and informing a user of the presence of the foreign material unless receiving the joining response signal.
However, in this prior-art approach, when the foreign material is detected in a wireless power transmission system, the user should remove the foreign material manually. Otherwise, the wireless power transmission efficiency may be deteriorated.